Reconstruction of sulfur metabolism in C. perfringens. We used the genomic data, growth assays and expression profiling to propose a tentative reconstruction of sulfur metabolism in C. perfringens. The cpe numbers for C. perfringens genes (strain 13) correspond to those of ClostriDB http://xbase.bham.ac.uk/clostridb/. The genes were renamed according to B. subtilis orthologues. The steps present in B. subtilis but absent in C. perfringens (sulfate assimilation and methionine biosynthesis by transsulfuration) are indicated by grey crossed arrows. A dotted arrow indicated the possible existence of a pathway. "?" indicates a step or a pathway for which a gene is lacking or remains to be identified. Serine O-acetyltransferase, cysE; OAS-thiol-lyase, cysK; anaerobic sulfite reductase, asrABC; glutamate-cysteine ligase/glutathione synthetase, gshAB ; SAM synthase, metK; adenosyl-homocysteine nucleosidase, mtnN; S-ribosyl-homocysteine lyase, luxS; cystathionine β-synthase, mccA; cystathionine γ-lyase, mccB. The following genes are absent from the genome of C. perfringens: metI (cystathionine β-synthase); metC (cystathionine β-lyase); metE (methionine synthase). AI-2, autoinducer 2; OAS, O-acetyl-serine; SAM, S-adenosyl-methionine; SAH, S-adenosyl-homocysteine; SRH, S-ribosyl-homocysteine. Ext means external.